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We studied the photon spectrum in coated microspheres with alternating quasiperiodic layers having left-handed (LH) materials included. It is found that the band gap (spectral zone of nearly zero transmittance) in such a system is strongly enhanced. At an increase of the quasiperiodicity parameter (QP), the boundaries of the spectral band gaps acquire intended shape. When QP exceeds the inverse golden...
We report first experimental evidences of spatial filtering of light beam in three-dimensional photonic crystals. The photonic crystals were fabricated in a glass bulk, where the refraction index was modified by applying femtosecond laser pulses. We observe the modification of the angular spectra (the far field) in the central maximum of the transmitted radiation in accordance with the theory of spatial...
A new type of terahertz (THz) photonic crystal waveguide is proposed and its dispersion characteristics are investigated. The cladding of this THz photonic crystal waveguide is silicon material containing periodic circular air holes arranged as triangular lattice, and the material of its core is polythene (PE). The band-gap distribution is studied by plane wave method (PWM), absorption boundary is...
In this work we are going to exploit k.p perturbation theory for calculation of momentum matrix elements and energy eigenvalue of semiconductors in general, and calculate the Ec & Ev the energy on conduction band and valence band respectively. Finally, we formulate the energy spectrum energy for II-VI material using the relation between the reduce mass μ* and the unperturbed band gap Eg0.
The functionalization and electric properties of graphene by the addition of transition metal atom of Ni to its surface had been investigated computationally using density functional theory with the generalized gradient approximation. The stable geometry adsorption position, binding energy, band gap, density of states, charge transfer of Ni adsorbed on graphene at two different coverages were calculated...
The refractive indices of (Al0.48In0.52As)z(Ga0.47In0.53As)1-z, and GaxIn1-xAsyP1-y quaternary materials is presented from a model that takes into account of band-to-band Coulomb interaction and Urbach broadening. We apply an accurate absorption model to calculate the contribution near band-edge region by a complete closed-form Kramers-Kronig transform. A Sellmeier-type single-oscillator model includes...
A novel hollow-core Bragg fiber structure with quasiperiodic dielectric multilayer cladding is proposed in near infrared (NIR) transmission. We theoretically demonstrate that the low loss transmission range of the HE11 mode can be significantly broadened by 450 nm.
Photonic Band Gap (PBG) materials [1,2] are artificial, periodic, dielectrics that enable engineering of the most fundamental properties of electromagnetic waves. These include the laws of refraction, diffraction, and spontaneous emission of light. Unlike traditional semiconductors that rely on the propagation of electrons through an atomic lattice, PBG materials execute their novel functions through...
The novel semiconductor material Ga(AsBi) is investigated by the time-resolved photoluminescence as function of lattice temperature, excitation density, and excitation energy. Disorder and localization effects are found to strongly influence the spectra and the dynamics.
InGaN LED efficiency depends significantly on current density, emission wavelength and junction temperature. Phosphor-converted blue LEDs are still more efficient than RGB multi-LED solutions despite inevitable Stokes losses: 104 lm/W at 350 mA have been demonstrated for a warm-white (TC = 2950 K) phosphor-converted blue InGaN LED with 1 mm2 chip size.
We report the first experimental demonstration of photonic bandgaps (PBGs) in 2D hyperuniform disordered materials and show that is possible to obtain isotropic, disordered, photonic materials of arbitrary size with complete PBGs.
A novel and facile synthesis route has been developed to prepare semiconductive In2O3 particles with hollow interiors and microporous shell structures. From the etching profile of XPS analysis, ??implantation?? of indium species into the polymeric templates occurs in C2Cl4 solvent, forming particles with a core-shell structure. Upon calcinations to 600??C, polycrystalline In2O3 hollow particles with...
A series of new blue emitting materials; 9,10-diotolylanthracene (1), 2-tert-butyl-9,10-diphenylanthracene (2), 10,10'-diphenyl-9,9'-bianthracene (3), and 1,4-bis(10-phenylanthracen-9-yl)benzene (4) were designed and synthesized for organic light-emitting diodes (OLEDs). In order to test the electroluminescent properties of 1-4, those were used as the host materials for the blue dopant materials,...
Fabrication of wide-bandwidth and highly reflective volume holograms is presented. Using holographic recording method, photonics structure as volume (Bragg) grating was created. Dichromated pullulan (exocellular homopolysaccharide) was used as a recording medium. A peculiar multi-peak structure in the reflection spectra is observed. It was found that appearance of a multi-peak phenomena leads to a...
We propose a methodology allowing the design of the active layer of organic solar cells in the shape of a photonic crystal. An optimised photonic crystal allows trapping the light in a layer at specific wavelengths thanks to a coupling of a low group velocity mode called slow Bloch mode. This method is used to design two structures which allow to improve absorption of light in organic solar cells...
The number of possible crystalline materials is vast and few have been explored as radiation detector materials. In this work we present an empirical approach for estimating band gaps, and Ce3+ and Eu2+ absorption energies of compounds using only their chemical formulas. The result would be useful in identifying candidate semiconductor detector materials (band gap between 1.5 and 2.5 eV) and Ce3+...
The number of possible crystalline materials is vast and few have been explored as radiation detector materials. In this work we present an empirical approach for estimating band gaps, and Ce3+ and Eu2+ absorption energies of compounds using only their chemical formulas. The result would be useful in identifying candidate semiconductor detector materials (band gap between 1.5 and 2.5 eV) and Ce3+...
Efficient atomistic simulators are required for full band treatments in strongly quantum confined systems, and for simulation of transport in emerging materials and devices such as graphene. Here we present an efficient transmission matrix based approach to ballistic quantum transport calculation for full three-dimensional, nearest-neighbor tight-binding based atomistic simulations. The method is...
Accounting for spectral hole burning, carrier heating and carrier density modulation, we investigate the wavelength dependence of the linewidth enhancement factor in semiconductor optical amplifiers excited by picosecond pump pulse.
Second harmonic generation efficiency in one-dimensional photonic crystals with material dispersion is calculated. The computational approach uses a shooting method to solve the wave equation for fundamental and second harmonic fields.
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